This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-249670 filed Aug. 21, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method of manufacturing methanol.
2. Description of the Related Art
The conventional method of manufacturing methanol (CH3OH) is as follows:
Natural gas having steam and carbon dioxide added thereto is supplied into a reaction tube of a reformer, the reformer being provided with the reaction tube loaded with, for example, a nickel-based catalyst, and a combustion radiation section for heating the reaction tube by the combustion of a fuel. In this case, the hydrocarbon in the natural gas reacts with the steam so as to generate a synthetic gas containing as main components hydrogen, carbon monoxide and carbon dioxide.
Since the steam reforming reaction described above is an endothermic reaction, the fuel is combusted in the fuel combustion section so as to heat the reaction tube.
The synthetic gas contained hydrogen, carbon monoxide and carbon dioxide is reacted in the presence of a methanol synthetic catalyst under a predetermined pressure and a predetermined temperature so as to synthesize a crude methanol.
The crude methanol is subjected to a gas-liquid separation for separation into a liquid crude methanol and a purge gas mainly containing hydrogen. The separated purge gas is recycled into the combustion radiation section so as to be utilized as a part of the fuel.
The liquid crude methanol recovered in the recovery process is distilled in one or a plurality of distillation towers so as to separate the crude methanol into a refined methanol and a waste water containing an organic compound having a boiling point lower than that of methanol (hereinafter referred to as a xe2x80x9clow boiling point organic compoundxe2x80x9d), an organic acid, and an organic compound having a boiling point higher than that of methanol (hereinafter referred to as a xe2x80x9chigh boiling point organic compoundxe2x80x9d).
Methanol is manufactured through the processes described above.
An object of the present invention is to provide a method of manufacturing methanol, in which a purge gas obtained by a gas-liquid separation of a crude methanol and mainly containing hydrogen is recycled to a natural gas having steam and carbon dioxide added thereto so as to utilize the purge gas as a part of the fuel, thereby increasing the methanol yield.
According to a first aspect of the present invention, there is provided a method of manufacturing methanol, comprising:
a synthetic gas forming step, in which a natural gas having steam and carbon dioxide added thereto is supplied into a reaction tube of a reformer provided with the reaction tube and a combustion radiation section for heating the reaction tube by the combustion of a fuel so as to bring about a reaction between the hydrocarbon contained in the natural gas and the steam, thereby forming a synthetic gas containing mainly hydrogen, carbon monoxide and carbon dioxide;
a crude methanol synthetic step for performing the reaction of the synthetic gas in the presence of a methanol synthetic catalyst so as to synthesize a crude methanol;
a gas-liquid separation step for separating the crude methanol into a liquid crude methanol and a purge gas mainly containing hydrogen; and
a distillation step for distilling the liquid crude methanol so as to separate a refined methanol;
wherein a part of the purge gas is recycled into the natural gas having steam and carbon dioxide added thereto in advance.
In the method of manufacturing methanol according to the present invention, it is desirable for a part or all of the carbon dioxide gas added to the natural gas to be the carbon dioxide recovered from at least one of the combustion waste gas generated from the combustion radiation section of the reformer and the combustion waste gas generated from the boiler for the steam generation.
In the method of manufacturing methanol according to the present invention, it is acceptable for a part of the purge gas to be recycled into the combustion radiation section of the reformer so as to be utilized as a part of the fuel.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.